Assertion : Nitride ion `(N^(3-))` and magnesium ion `(Mg^(2+))` are both isoelectronic species.
Reason : the charge on nitride is different from `Mg^(2+)` ion.
A. If both assertion and reason are correct and reason is correct explanation for assertion.
B. If both assertion and reason are correct but reason is not correct explanation for assertion.
C. If assertion is correct but reason is incorrect.
D. If both assertion and reason are incorrect.